1. Technical Field
This invention relates to a surface emitting semiconductor laser, a method for fabricating a surface emitting semiconductor laser, a module, a light source apparatus, a data processing apparatus, a light sending apparatus, an optical spatial transmission apparatus, and an optical spatial transmission system.
2. Related Art
In technical fields such as optical communication or optical storage, there has been a growing interest in surface emitting semiconductor lasers, i.e., Vertical-Cavity Surface-Emitting Lasers (hereinafter referred to as VCSELs). VCSELs have excellent characteristics which edge-emitting semiconductor lasers do not have. For example, VCSELs feature lower threshold current and smaller power consumption. With VCSELs, a round light spot can be easily obtained, and evaluation can be performed while they are on a wafer, and light sources can be arranged in two dimensional arrays. With these characteristics, demands for VCSELs as light sources in the communication field have especially been expected to grow.
In a case where a VCSEL is used as a light source or the like for optical transmission, selection of mode of laser light is required. For example, in a case where a VCSEL is coupled to an optical fiber and a long-distance communication is to be performed, single-mode is more preferable. To obtain single-mode, in general, it is required to make the diameter of a current confining layer of the VCSEL to about 3 to 4 micrometers.
For a VCSEL of a selective oxidation type, AlAs or AlGaAs having a high Al-composition is used for the current confining layer, and a portion of the current confining layer is oxidized to form an aperture in the current confining layer, and a portion of the current confining layer is oxidized to form an aperture in the current confining layer. Because the aperture is formed by an oxidizing reaction of Al, it is difficult to accurately control the diameter, and especially, it is difficult to reproduce a small aperture diameter for obtaining single-mode, resulting in a reduction in yield of the VCSEL.
The present invention aims to provide a surface emitting semiconductor laser in which mode control can be performed more effectively than the mode control by surface processing of a light emitting surface of a related art, and a module, a light source apparatus, a data processing apparatus, a light sending apparatus, an optical spatial transmission apparatus, and an optical spatial transmission system, which use the surface emitting semiconductor laser, and a method for fabricating a surface emitting semiconductor laser.